Process of making activated carbon



Patented May 11, 1948 2,441,125 PROCESS OF MAKING ACTIVATED CARBON Ernst Ber], Pittsburgh, Pa; Walter G. Berl as executor of said Ernst Berl, deceased No Drawing. Application September 23, 1942, Serial No. 459,438

Claims. 1

This invention relates to processes of manufacturing activated carbon, particularly briquetted activated carbon.

While activated carbon is useful for many purposes, e. g. for the dechlorination of over-chlorinate'd water and for decolorization of sugar solutions, there is a great demand for it at the present time for the adsorption of vapors and gases, especially poisonous gases that may be used in chemical warfare and poisonous or solvent vapors that escape during industrial operations. For these purposes carbon in hard lumps of different particle sizes are desirable, if not necessary. Carbon produced from nut shells or hard wood can be manufactured with the preferred particle size and hardness. However, activated carbon in powdered form is produced in large quantities, either as a by-product of the processes of making the granular activated carbon or by special processes such as disclosed in my United States Patents No. 1,812,316 and No. 1,851,888..

In order to use such powdered carbon for gas adsorption and for dechlorination of water and decolorization or other purposes, it may be desirable that the active carbon be formed into dense lumps of special shapes and sizes by a briquetting process and without reducing the adsorption capacity of the carbon per unit of weight. In replacing the light powder by dense pieces of desired geometric form, one gets increased adsorption capacity per unit of volume. The special geometric form, e. g. saddles, cylinders, etc., allows a lowering of pressure drop within the space filled with this formed activated carbon. This is of great importance for mouthpieces of gas masks and for industrial uses, e. g. recovery of solvent vapors. I

When used for adsorbing solvent vapors incident to industrial operations such as the manufacture of rayon, smokeless powder, recovery of gasoline from natural gas, artificial leather, etc., these briquetted carbons are subjected to higher temperature, often above the boiling point of water, for example during steaming of material that contains adsorbed vapors or by drying the wet steamed carbon with hot air. Therefore, for this briquetting process it is necessary to use as binders substances which will not melt or decompose at or below such high temperature. The best way to carry out such a briquetting process is to use a binding material which in itself has active properties; in other words, active carbon may play the role of such a cementing material. In addition to these requirements for a satisfactory binder, other difiiculties have been encountered in bind the particles of this strongly hydrophobic material together strongly enough. Gas films on the activated carbon particles may be the reason for this behavior. When certain briquetted activated carbons are submitted to different temperatures, they are converted into fine powder. In other cases, the binder used substantially reduces the activity of the carbon. This is due to the fact that decomposition products of the hinder, for instance pitch or starch, at higher temperatures form non-active, graphitic carbon which contains little bound hydrogen and oxygen. This so-called secondary carbon covers the active places of the real active carbon ously aifects its activity.

Furthermore, the great demand for activated carbon requires that new and additional sources of raw materials be found to provide an adequate supply of activated carbon of desired qualities and at reasonable cost; and this in turn necessitates new or improved methods of treating the raw materials during this conversion process in order to get activated carbons which show a maximum adsorption capacity towards vapors, poison gases, dye stuffs and which react quickly and efiiciently with those conversion compounds of halogens which are formed by the reaction of halogens with chlorinated water, e. g. hypochlorous acid.

Therefore prime objects of my invention are to provide a novel and improved method of'producing activated carbon, whereby numerous carbonaceous raw materials may be utilized to make a powdered activated, partly hydrophobic intermediate product; and to provide a new and improved method for forming said intermediate product at low cost into lumps of desired shape and particle size that will be retained after the conversion of this intermediate product into highly activated carbons which fulfill the requirements for gas adsorption, water dechlorination or decolorization operations, etc. I

Another object of my invention is to provide a novel and improved method of briquetting intermediate products and powdered activated carbon including the utilizationof new and especially effective binders, whereby the adsorption properties of the carbon shallnot be deleteriously affected and briquets or lumps shall be capable of withstanding high temperatures, pressure and wear without disintegration.

Other objects, advantages and results of myinvention will appear from the following description.

and deleterificatlon process carried out between 300 and GQQT" 0. Then for briquetting the by adding a finely powdered binder, such as a phenol formaldehyde resin, heating, the mixture at temperatures or from 130 to zgp f pguuder- QOWS Qlf I. Pleased high pressure, e. g. 500 to 19,0( p. s. i., thereby Y polymerizing the resin;

during or before this polymerization operation shaping the mixtureinto lumps or particles of the desired form, -e.g small rods, saddles, plates, disks, cylinders, balls, and thee t n the formed m al to temps betweenwllfqandizoc?C. More X articularly. describing the invention, it ma be pointed out thatduring the Dre-active.-

O d fiie eet ma e a t tem e a ure be ween wilt-and 509 Q. the material itself goes often through a plastic stage. During. this. plastagea simultaneous development of gascorn- 99 carb n ioxidawater and. or anic. c mpqungiseernethane and hems es e c-'tekes his??? Msl e lesseorous mater al results alter llie e eleeme i gas .v a d vasersha reac ed is en It isa etea u ic h at t e mater a with as t be a ti ated. n re sure or n the ab cess act v t n en t em r tu s above. thes tem e atu es here t e plastic stage exists and to maintainthese tempeta -lu e u i h dev l m nt. 9i ra k leases has-ceas d. coo ing he. materia res a-mere 9: less ps-m r li ht Wei ht. llhis massyvhich. is b ittl a mqm te e atur l er sde lar r li l swhiell a res ons ble i t very l ht weieb 'ars pene llPWlh de w th h r a aren K it results.

h s materia roduced ro sale ar present i "th uirin th rre-a t'iv .iqn alr a 99.nt subs anc for ns an e. retesa s sm sulfii r as ure t ovate-esteem area. pres es c anide e a fitness. acti atin bstances e add st wards.

,Bstassium su fatesl s eptassium su fit ac a tanneratures abore .09) Q oxid z ng n so he ma e i s T b r a osr rteda temer 9 1998 4. 9"?- e se 9 ar en sul leis potassirm ulfidea si m sulfate and masses. salut produce rem the es t ng in ermed te prod ct' a t ed rbons w h laser a pa nt dens t a d emewh larg capillaries so that vapors of substances with hi he mus ular we h or instance chl e. .ea er the e caeilla The Yield in er qeis low r in; chambers? y ea si also t ea u tv towa 1 52 an similar deri at l qd ne-j l ulfide e e ac ates 1 bstansa am neithe ntermed ate product obta1ned,,. ,Wfill $39-$99 Q; i th a t vi ies. temperature bet e .8 n 2 are class as is t ea e h mu um fate. I-i-iere is no ozidizing action by bound oxys an f ill- Pi es uwa material,ig -the coalified product to the potassium preferably gen. Therefore, yields in activated carbon are increased, finer capillaries are produced so that vapors of higher molecular substances cannot enter very easily into these fine capillaries and be retained. The apparent density of the resulting activated carbons is somewhat higher than those which are produced in the presence of largen amounts; of potassium sulfate. The decoloriz-ing power is not as high as with the potassiumsulfate activated carbon.

' By controlling the amount of the added potassalt audits oxygen content in the mixture which has to be submitted to 890-1209 (7., i. e., between the organic content and the oxygen content of these potasslum compounds, it is possible to obtain different carbons in powder form or in form of larger, harder lumps with different apparent densities, difierent yields and dififerent adsorption and decolorizellion DOW? If briguetted material has to be produced, the binder is added to the intermediate product obtained at emperatures between 3550 and 600 0. either with or after the addition of potassium $34 For this binder such material should be used which at high temperature decomposes and itself forms through reaction with the potassium salts present activatedcarbon which cements togather the activated carbon produced from the ground mass. Very hard and dense particles of any desired geometric shape can be obtained in this way, It been found that phenol forma dehyde resins, urea formaldehyde resins, resins with the basis of melamine, and similar resins are best suited ior this purpose.

It is important that the material which has been partly degasified previously at moderate temperatures (BOG-600 C.) in order to get more densematerial afterwards, should contain a certain amount of bound oxygen; in other words, it should have certain hydrophilic qualities. Under those conditions it is necessary to use only rather small amounts, 5-3G%, of the right kind of binding resin to obtain the desired results.

Qom'pletely activated carbons with very little bound oxygen and hydrogen, due to the gas films formed on'their surface and to their hydrophobic qualities, need more binder than the partly hydrophilic intermediate product produced at 300- 690" G. One has to add also potassium compounds to this mixture of hydrophobic activated carbon and binder so that the following activation at elevated temperature (800-1200" C.) produces activated, cementing carbon from the binder material itself,

The preheated, partly hydrophilic, finely powdered, practically non-active material and, if necessary; another amount of activating substances,

potassium compounds, are mixed intimately with the finely powdered binder, for instance phenol formaldehyde resin. The resulting finely pulverized and thoroughly mixed ma terial is formed into any geometric shape while it is submitted to higher temperature under pressure; this in order to avoid the formation of larger holes caused by the formation of steam and decomposition products produced from the polyplus the activating substances, for instance potassium compounds.

The resulting, very-hard and dense material is then subjected to higher temperatures between 800 and 1200 C., preferably to about 950 C.

in absence of free oxygen. This can be done at normal, reduced or increased pressure. Then an activation process takes place without great change of the structure and the dimensions of the previously briquetted material. Inorganic, oxygen-containing material, for instance potassium sulfate or potassium sulfite, is'reduced to potassium sulfide. This newly produced and for merly added potassium sulfide also acts as potassium-salt activator.

phitic compounds CaK and CieK which decompose with water. They are responsible for part of the activation reaction. Sulfur present corrodes the surface of the newly produced, small crystallites by the formation of carbon disulfide,.:

contributes to the activation process. About 50% of the weight of the dry resin is converted into an activated carbon which cements together the activated carbon particles resulting from the activation of the organic material.

The specific steps of the process may be varied as will be apparent from the following examples:

EXAMPLE 1 Water-soluble acid sludge from the oil refineries after separation of the free sulfuric acid present by the addition of 50-200% of water is converted by the addition of alkaline potassium compounds, for instance potassium hydroxide, potassium carbonate, potassium sulfide, etc, into the corresponding neutral potassium salts. According to the more or less complete separation of free sulfuric acid, less or more potassium sulfate may be formed also. The resulting neutral salts are then partly decomposed by heating them .to temperatures between 300 and 600 C., preferably to about 400-450 C. There results a rather light powder which contains, besides organic substances, smaller amounts of water-insoluble potassium compounds bound chemically with the organic material and larger amounts of water-soluble, free potassium salts, mostly potassium sulfate. This powder can be used as such for further operations. If necessary or desired It forms potassium-gra-:

one may extract all or some of the potassium sulfate or add more of it. With or without the extraction of part or all of the potassium sulfate, potassium sulfide (KzS) or other potassium compounds free of or poor in bound oxygen, e. g. potassium cyanide, potassium sulfocyanide, potassium cyanate, may be added. The organic substances which are formed by the coalification between 300 and 600 C. contain enough hydrophil oxygen-containing groups so that the resulting material wets rather easily with water and does not adsorb much gas. The activity of this brown, organic residue is very low.

This material must be ground to very fine particle size inorder to open the larger holes which have been formed by the development of gases through the previous heating. Then to this mixture finely powdered organic resins, for instance phenol formaldehyde resins are added. According to the fineness of the powder and its nature, 5-30%, preferably 712%, of phenol formaldehyde resins are used. The phenol formaldehyde resins may be utilized also in dissolved form,

This mixture of organic material plus potassium compounds with bound sulfur and phenol resin is then converted into the B and C resin stage by a treatment under pressure (1000- 10,000 p. s. i.) at temperatures between and 250 0., preferably at about 180 C. Through the polymerization of the phenol resin a perfect cementing of the organic material and potassium salts takes place. During or before this polymerization operation under pressure, the mixture can be converted into the desired geometric form, for instance into disks, plates, rods, cylinders, saddles, balls, etc.

The now resulting material must be submitted to activation temperatures between 800 and 1200 0., preferably between 900 and 1000 0. Then many reactions take place. At this high temperature a rearrangement of carbon atoms under formation of a graphite lattice occurs. The potassium compounds act as activating substances. They corrode the graphite-like material. Free, unsaturated valences are formed, as are also finer and coarser capillaries, in this now resulting material which is poor in bound oxygen and hydrogen. During this activation process the phenol formaldehyde resin in the presence of the potassium compounds is also converted into graphitic but active carbon which cements the carbon particles together.

Without change in the external structure of the previously formed material, activated carbon with excellent properties results. The following table shows the results of an accelerated chloropicrin test (49 mg. chloropicrin per 1000 cu. cm. and. 1000' cu. cm. of air-chloropicrin mixture per sq. cm. and min.) Activated carbon made in the described way from water-soluble acid sludge is compared with gas mask carbon made from cocoanut shell as follows:

' are formed.

particle size, for

cr me-activated carbon to about 500-700 C. or

litzcan'be seen from-these'resultstthatthe activated i gas adso'rbin'g carbonv on a volume band -weightrbasis is superior to-"gas 'carbonszemade resins asusedin Example. 2'," "resins'wi'th the basis of melamine present similar results.

EXKMPLE 4 'Fot-assium salts of :water-soluble acid=jsludge are mixedaccording -to-U.--"S. Patent 1,851,883,, with wood chips, dBIlSeTWOd,OI lignites or" bituminous coals. =This intimate cmixture vto which; if; necessary; potassiumsulfate orapotassium sulfite, or potassium sulfide may be added, is heated to temperatures of about 300-600?'C.,,. preferably between 40d and 4.50" .C.,-in order to carryout the first step of a coalificationprocess during which large'amounts of coalification gases After having carried out. the decomposition process at this moderate temperav --iby theizextraction "with organic or inorganic solvents increases the adsorption "capacity-tok'wardsyapors and dissolved dyestufi =molecu1es iabout:-51-"20%.

' The resulting activated carbon. gives results "similar-to:those' describedin Table-I, Example 1.

EXAMPLE Dense woodor lignite is mixed with potassium gum:sulfatersolutionso that the dry mixture con- .tains between and 60% of potassium sulfate -..or potassium sulfide. This mixture is brought to temperatures up to 550 C., preferably between 400. and-450 C. The resulting coalified mass is pulverized so thatlarge holes, caused by the developmentofgas during the plastic stage are yopened. I This material then is mixed withartificial resins described in Examples 1, 2,-and- 3. -Briquettingand heating processes are the same ;as described in Examples 1- and 4. The result- ;ing potassium sulfide after the formation of activated' carbon has taken place at high temper ature, has to be removed by a systematic extraction with water. The activated carbon after 53 havingbeen briquetted or not may be submitted to a second heating process or extraction process as describedin Example 4.

EXAMPLE 6 "To waste sulfite liquor resulting from theproture, the material is ground up tovery line duction of 'sulfite P Potassium Carbonate instance less than 200 "mesh. The material may be :used as it is or further amounts of potassium sulfate, or potassium sul- "a fine "powder. or in watery solution is added until the whole amount of calcium salts of lignin sulfonic acids is converted into water-soluble fide, or mixtures of potassium sulfate and potas- D p u d The resulting solution .added. To this very intimate mixture, resins as' described in Examples 1,-2and3 areaddeddn sufficient quantity, either in solid or in dissolved form. The mixture of coalified material, potassium salts and resin binder is 'then--subjected to, higher temperature HBO-250 .C.) and pr'essure (SOD-10,000 p. s. i.) and the formation of appropriate geometric forms may be carried out. This material should be subjected, preferablyin the absence of oxygen, to temperatures between 800 of these potassium compounds is separated by sedimentation "or'filtratio'n from the precipitated calcium carbonate. One may add to thiss'olution' potassium sulfate or potassium sulfide in order to change the activity of the finally resulting activated carbon. The neutral or alkaline liquid is then dried.

As hereinbefore stated, the qualities of the activated carbon can be regulated or varied by .varying the ratio of potassium ,to organic sub- :stance and by controlling the ratio of oxygen .:bound on the potassium compounds to the. organic substance. Most of the potassium is chemically bound in this mixture as potassium salt vof lignin'sulfonic acids. If desired, potassium and 1200 'C., best between 900'and'1000" C. The Sulphate pfita'ssimlli sulp'hite, st ces w th cooled, the resulting K28 is extracted with water 55 It maybe used for the neutralization of another batch of waters'oluble acid sludge. The then resulting hydrogen sulfide may beconvertedinto sulfur, or sulfuric a'cid, oroleum.

The resulting activated carbon :may -be extracted, if necessaryor'desired, with diluted by molecules dissolved in liquids.

" movingsulfur' which 1 is 'formed -tfrom'the: decomposition of polysu lfides. This i sulfur otherwise occupies part of the active; placesi'oflthe gas carbon. The adsorbed sul iflurcan tbe removed also by any solvent fonit, for instance warm benzene, dichlorbenzene, or watery sodium sul- -.fite solutions.

' The removaliof the adsorbed sulfur byiheating material is a relatively large amount of bound oxygen, may added to the dry material, or sulfide, cyanide or suliocyanide of potassium having no bound oxygenmay be added.

Using. more potassium sulfate reduces the .fin'aliyield in -active carbon, decreases theap- Hparentdensity which may go down to .06land increases the. adsorption capacity toward larger 'gasmolecules and largermole'cules like dyestuff Increasing the amount. of. potassium sulfide increases the yield ..andiapparent density,,decreases somewhat the adsorption capacity toward larger-I gas-molecules withoutirifiuencing the adsorption capacity for 5 smaller gas molecules, and decreases somewhat the adsorption capacity towards larger molecules, -or-instance dyestuff molecules, dissolved in liquids.

The coalification steps come next. The dry subjected to temperatures between 300 and 600 0., best between 400 and 500 G. Then' many processes take place. The carboifihydrates present in the used waste sulfite liquor sarerconverted into potassium salts of saccharinic ...-75.-acids. Those saccharinic acid potassium salts the described way from water-soluble acid sludge is compared with gas mask carbon made from cocoanut shell as follows:

Table II Mg. chloro- Mg. chloro- Apparent picrin adpicrin addensity, sorbed by 1 Ratio sorbed by 1 Ratio g./ml. mLactive gr. active carbon carbon Waste sulfite pulp carbon 362 316 100 873 100 Oocoanut shell carbon I 42 252 80v 600 B8. 5 Cocoanut shell carbon IL 45 225 71 500 67 During a certain temperature interval begmmng EXAMPLE 7 at about 150 C. a large formation of gases takes place. After the development of gas has ceased, a foam-like material results which must be pulverized. To the now resulting material a binder and potassium salts may be added. Oxygencontaining potassium salts may be partly or completely removed by extraction with water and replaced partly or completely by oxygenfree potassium salts, for binding and formation of the desired geometric structures at elevated temperatures and pressures takes place according to Examples 1 and 4. The now briquetted material is heated, according to Examples 1 and 4, to temperatures between 800 and 1200 0., best at 900-950 C. The treatment of the resulting activated carbon, which retains the former geometric shape, is carried out according to Examples 1 and 4. Again an excellent briquetted material results which is. as

useful for gas mask purposes. Excellent activated carbons for dechlorination and decolorization of liquids can be obtained and used where a granular or otherwise larger sized activated carbon may be desired.

If desired, the incoalification may be carried" out in one step by heating the potassium salts of the lignin sulfonic acids and other compounds in the neutralized waste sulphite liquor, to a example KzS. The.

20 bohydrates are present. The latter can be separated from the lignin compounds either by fermentation or by osmosis. It is advantageous to submit the material obtained after treatment with potassium carbonate to these processes of fermentation or osmosis. The resulting material with little or no sugars has to be submitted to the same treatment as described in Example 6. The osmos sugars may be used eiher as such or as raw material for fermentation. Ethanol, acetone,

butanol, citric acid, glycerine and other fermentation products may be obtained.

What I claim is:

1. The steps in a process of making activated carbon, comprising converting the calcium compounds of waste sulfite liquor from the production of sulfite pulp with potassium carbonate into the corresponding potassium compounds, separating the calcium carbonate from the watery liquid, evaporating the solution to dryness, heating the dry residue to 300-600 C., extracting from said residue water-soluble potassium salts at least partly, afterwards intimately mixing the intermediate product with a controlled amount of at least one water-soluble potassium compound betemperature of from 800-1200 C. preferably; ing a member of the group consisting of potassium 900-950 C. Then many reactions take place. Internal combustion forms large amounts of carbon dioxide, water, hydrocarbons, and other volatile substances. About of the sulfur bound originally in the form acids is converted mostly into S02 and into free sulfur. Potassium sulfate and potassium sulfite formed at moderate temperatures (300-600" C.) from the potassium salts of lignin sulfonic acids and the potassium sulfate and potassium sulfide which have been added intentionally lose at the activation temperature (800-1200 C.) their oxygen and corrode strongly during their conversion into K28 the graphitic activated carbon.

Small amounts of metallic potassium are formed 0 which subidivided as compounds like 08K and 016K the graphitic crystals into units which contain only a few planes.

During this heating to 800-1200 0., preferably to 900-950 C., practically all potassium salt pres- 5 ent is converted into potassium sulfide.

After extraction of the water-soluble material (K28), an excellent activated carbon is obtained. Without change in the external structure of Sulfide,'potassium sulfite, potassium sulfate, potassium carbonate, potassium cyanide and potassium sulfocyanide, coalifying the mixture at temperatures'from 800-1200 C., and extracting said of lignin'sulfonic 50 water-soluble potassium compounds; whereby by increasing the ratio of chemically bound potassium to organic substance in said intermediate product fine capillaries are produced in the final product, and by increasing-the ratio of chemically bound oxygen toorganic substance in said intermediate product the apparent density of the final product is lowered.

2. The steps in a process of making activated carbon, comprising converting the calcium compounds of waste sulfite liquor from'the production of sulfite pulp with potassium carbonate into the corresponding potassium compounds, separating the calcium carbonate from the watery liquid, evaporating the solution to dryness, heating the dry residue to 300-600 C., extracting from said residue water-soluble potassium salts at least partly, afterwards intimately mixing the intermediate product with a controlled amount of at least one water-soluble potassium compound bethe previously formed material, activated carbon ng a member Of the g p consisting of P tassium with excellent properties results. The following table shows the results of an accelerated chloropicrin test (49 mg. chloropicrin per 1000 cu. cm. and 1000 cu. cm. of air-chloropicrin mixture per sq. cm. and min).

Activated carbon made in sulfide, potassium sulfite, potassium sulfata potassium carbonate, potassium cyanide and potassium sulfocyanide, coalifying the mixture at temperatures from 800-1200 C.,and extracting said water-soluble potassium compounds and removing :11 adsorbed sulfur; whereby by increasingtheratioof chemically bound potassium toiorganic substance in said intermediate product finercapillaries are produced in the final product, and by increasing the ratio of chemically bound oxygen to organic --substance in said intermediate-product the apparent density of the finalproduct is lowered.

3.-The steps in a process of making activated carbon, comprising converting the calcium compounds of waste sulfite liquor from the production of sulfite pulp with potassium carbonate into the corresponding potassium compounds, separating lthe calcium carbonate from the watery rliquid, evaporating the solution to dryness, heating the dry residue to 300 600 0., extracting from said residue water-soluble potassium salts at least partly, afterwards intimately mixing the inter- -mediate'product withalcontrolled amount of at least: tonecwater-solublelpotassium compound beaiugaaimember of the group consisting of potassium -s.u1fide,i.potassium 'sulfite, potassiumw sulfate, potassium. carbonate, potassium cyanide and poltassium suliocyanide, and with a resin binder, forming the mixture into the desired geometric .form and heating it to a temperature of from 110-2509Crat a .pressure from about500 to 10,000 --p. s, i., and heating the resulting product at tem- --peratures from 800-1200 13., and extracting said water-soluble potassium-compounds; whereby by increasing the ratio of chemically bound potassium to organicsubstance in said intermediate product fine capillaries are produced 'in'the final product, and by increasing the'ratio-of chemically bound oxygen to organic substance insaid intermediate product the apparent density of thefinal product is lowered.

4,-The steps in a process of making activated carbon, comprising converting the calcium compounds of waste sulfite liquor from the production of .sulfite pulp with potassium carbonate intothe corresponding potassium compounds, separating the calcium carbonate from the watery liquid, evaporating the solution todryness, heating the dry-residue to 300-600. 0., extracting from said residue water-soluble potassium saltsat least partly afterwards intimately-mixing the intermediate product with a controlledamount of at least one water-soluble. potassium compound be ing a member-f the group consistingof potassium sulfide, potassium sulfite, potassium sulfate, potassium carbonate, potassium-cyanide and potassium, and with a resin binder, forming the mixture into the desired geometric form, and heating it to a temperature-of-from 1l0-250 C.

ata pressure from about 500-10,000 p s i., and

heating the resulting product-at temperatures from 800-1200 0., and extracting said water- ;soluble potassium compounds and removing adsorbed sulfur; whereby by increasing the ratio of chemically bound potassium to organic substance insaid intermediate product fine capillaries are produced in the finalproduct, and by increasing .theratio ofv chemically bound-oxygen to "organic substance in said intermediate product theap- =parent density of the final product is lowered.

I :5. The steps in a process of making activated carbon,--comprising converting the calcium compounds of waste sulfite liquor from the production of sulfite pulp with potassium'carbonateinto the corresponding potassium. compounds, separating the calcium? carbonate: from the watery liquid, evaporating the solution to drynesaheating the dry residue to '300-600.C., extracting from said residue water-soluble potassiumsalts .at' leastpartly, afterwards:intimatelymixing the intermediate product -with potassium 1 sulfide,

"coalifying the mixture at temperatures from-800 -l200 C.,;and extracting said potassium sulfide; whereby by increasing the ratio of chemically bound potassium to organic substance in said intermediate product fine capillaries are produced 7 carbon, comprising converting the calcium compounds of waste sulfite liquor from the production of sulfite pulp with potassium carbonate into the corresponding potassium compounds,

separating the calcium carbonate from the watery liquid, evaporating the solution to dryness, heating the dry residue to 300-600" (3., extracting from said residue water-soluble potassium salts at least partly, afterwards intimately mixing the intermediate product with potassium sulfide, and with a resin binder, forming the mixture into the desired geometric form, and heating it to a temperature of from 100-250 C. at a pressure from about EGG-10,000 p. s. i., and heating the resulting product at temperatures from 800-1200 0., and

extracting said potassium sulfide; whereby by increasing the ratio of chemically bound potassium to organic substance in said intermediate product fine capillaries are produced in the final product, and by increasing the ratio of chemically bound oxygen to organic substance in said intermediate product the apparent density 'of the 'final'product is lowered.

'7. The steps in a process of making activated carbon, comprising converting the calcium compounds of waste sulfite liquor from the production of sulfite pulp with potassium carbonate into the corresponding potassium compounds, separating the calcium carbonate from the watery liquid, evaporating the solution to dryness, heating the dry residue to 300-600 C., extracting from said residue water-soluble potassium salts at least partly, afterwards intimately mixing the intermediate product with potassium cyanide, coalitying the mixture at temperatures from 8001200 C., and extracting said potassium cyanide; whereby by increasing the ratio of chemically bound potassium to organic substance in said intermediate productfine capillaries are produced in the final product, and by increasin the ratio ofchemically bound oxygen to organic substance in said intermediate product the apparent density of the final product is lowered.

8. The steps in a process of making activated carbon, comprising converting the calcium compounds of Waste sulfite liquor from the production of sulfite pulp with potassium carbonate into 'the corresponding potassium compounds, separating the calcium carbonate from the watery liquid-evaporating the solution to dryness, heating the dry residue to 300600 0., extracting from said residue water-soluble potassium salts at least partly, afterwards intimately mixing the intermediate product with potassium cyanide,

and with a resin binder, forming the mixture into the desired geometric form, and heating it to a temperature of from 1l0-250 C. at a pressure from about 500-10,000 p. s. i., and heating the resultingproduct at temperatures from 800-1200 C., and extracting said potassium cyanide; whereby by increasing the ratio of chemically bound potassium to organic substance in said intermediate product fine capillaries are produced in the final product, and by increasing the ratio of chemically bound oxygen to organic substance in said intermediate product the apparent density of the final product is lowered.

9. The steps in a process of making activated carbon, comprising converting the calcium compounds of waste sulfite liquor from the production of sulfite pulp with potassium carbonate into the corresponding potassium compounds, separating the calcium carbonate from the watery liquid, evaporating the solution to dryness, heating the dry residue to 300-600 0., extracting from said residue Water-soluble potassium salts at least partly, afterwards intimately mixing the intermediate product with potassium sulfocyanide, coalifying the mixture at temperatures from 800- 1200 0., and extracting said potassium sulfocyanide; whereby by increasing the ratio of chemically bound potassium to organic substance in said intermediate product fine capillaries are produced in the final product, and by increasing the ratio of chemically bound oxygen to organic substance in said intermediate product the apparent density of the final product is lowered.

10. The steps in a process of making activated carbon, comprising converting the calcium compounds of waste sulfite liquor from the production of sulfite pulp with potassium carbonate into the corresponding potassium compounds, separating the calcium carbonate from the Watery liquid, evaporating the solution to dryness, heating the dry residue to 300-600 C., extracting from said residue water-soluble potassium salts at least partly, afterwards intimately mixing the intermediate product with potassium sulfocyanide,

and with a resin binder, forming the mixture into the desired geometric form, and heating it to a temperature of from -250 C. at a pressure from about 500-10,000 p. s. i., and heating the resulting product at temperatures from 800- 1200 0., and extracting said potassium sulfocyanide; whereby by increasing the ratio of chemically bound potassium to organic substance in said intermediate product fine capillaries are produced in the final product, and by increasing the ratio of chemically bound oxygen to organic substance in said intermediate product the apparent density of the final product is lowered.

ERNST BERL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

